Perhaps you should try some spelling variations:
phuong tinh » phuong trinh, phuong binh, khuong tinh
hieu quang » thieu quang, hieu quan, hieu qua
hanh trang » thanh trung, canh tranh, hanh trinh
hieu sang » chieu sang, hieu lang, nhieu tang
cua dung » cua dong, qua dung, cua rung
cua dang » cua cong, cua ban
toan tap » toan ban

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((hieu sang) or (hieu quang)) - hanh trang ((cua dung) OR (cua dang)) phuong tinh toan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu quang)) - hanh trang ((cua dung) OR (cua dang)) phuong tinh toan tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sang) or (hieu quang)) - hanh trang ((cua dung) OR (cua dang)) phuong tinh toan tap".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu quang)) - hanh trang ((cua dung) OR (cua dang)) phuong tinh toan tap*.